1. Field of the Invention
The present invention relates to a dye-containing curable composition favorable for forming a colored image of a color filter used for liquid crystal displays and solid state image pick-up elements, a color filter such as electroluminescence color filters, and a method for producing the same.
2. Description of the Related Art
A dyeing method, an electrodepositing method, a printing method and a pigment dispersing method have been known for producing a color filter used for liquid crystal elements and solid state image pick-up elements.
In the dyeing method, a dyeing substrate comprising natural resins such as gelatin, glue and casein, or a synthetic resin such as an amine-modified polyvinyl alcohol is dyed with a dye such as an acid dye to produce a color filter.
However, the color filter described above involves a problem in light fastness, heat resistance and moisture resistance since the dye is used in the dyeing method. Moreover, irregular coloring is liable to occur since it is difficult to uniformly control dyeing adhesivity of the dye in forming a filter for a large size screen. While the production process becomes complicated because a dye-preventive layer should be provided for dyeing.
The electrodepositing method is such a method for producing a color filter in that a transparent electrode is previously formed in a prescribed pattern, and a resin containing a pigment dissolved or dispersed in a solvent is ionized, to which a voltage is applied to form a colored image in the form of the pattern.
In the electrodepositing method, a photolithographic process containing film formation and etching for the transparent electrode is necessary in addition to a transparent electrode for displaying. In the case where an electric short circuit is formed at this time, line defects are formed to cause reduction in yield. Furthermore, patterns other than stripe patterns, for example, mosaic patterns, are difficult to be applied in principle, and also, there is such a problem in that the transparent electrode is difficult to be handled.
The printing method is a simple method for producing a color filter by printing, such as offset printing, by using ink formed by dispersing a pigment in a thermosetting resin or an ultraviolet ray curable resin. However, an ink that can be used has a high viscosity to make filtration difficult, whereby defects are liable to occur due to dusts, foreign matter and gelled matters of the ink binder, and there are problems in positional accuracy, line width accuracy and surface smoothness associated with printing accuracy.
The pigment dispersing method is a method for producing a color filter by a photolithographic process using a colored radiation sensitive composition containing a pigment dispersed in various kinds of photosensitive compositions. This method is stable to light and heat owing to the use of the pigment, and sufficient positional accuracy is ensured since patterning is carried out by a photolithographic process. Therefore, it is a method suitable for producing a color filter for a large size and high definition color display.
As the pigment dispersing method, Japanese Patent Application Laid-Open (JP-A) No. 1-102469 discloses a negative-type photosensitive composition comprising a photopolymerizable monomer and photopolymerization initiator together in an alkali-soluble resin. However, although the color filter for the solid state image pick-up element has been required to be further fine in recent years, resolution of the color filter cannot be essentially improved since the pigment is dispersed as granules with a certain diameter by conventional dye dispersion methods. It was also a problem that irregular coloring tends to be generated due to coarse particles of the pigment. Accordingly, the pigment dispersing method was not suitable for uses requiring a fine pattern as in the solid state image pick-up element.
For attaining high resolution of the color filter, a technology such as the dyeing method using the dye as a colorant has been investigated. Examples of the dye-containing curable composition using the dye include a positive-type photosensitive composition using a naphthoquinone diazide compound as a photosensitive compound as disclosed in JP-A No. 2-127602, and a negative-type composition comprising a photopolymerization initiator (with a cross-linking agent) as a photosensitive compound as disclosed in JP-A No. 6-75375. However, solubility of the dye in solvents is a problem in these dye-containing curable compositions with an additional problem of low heat resistance and light fastness of the dye.
In relation to the problems above, the phthalocyanine compound may be used as the dye excellent in heat resistance and light fastness. However, it is a practical problem that solubility of the phthalocyanine compound in the solvent is poor. On the contrary, increasing the solubility in the solvent causes another problem of decrease of heat resistance and light fastness. Consequently, dye-containing curable compositions having good heat resistance and light fastness using a dye provided with good solubility in the solvent as well as heat resistance and light fastness, and color filters using the compositions, have not been available yet.
For example, JP-A Nos. 3-195783 and 2-276866 disclose sulfonic acid amide-substituted compounds and tetrazaporphyrin compounds as phthalocyanine compounds having improved solubility in solvents. However, since these compounds have a maximum absorbance wavelength in the range of 650 to 670 nm, they cannot exhibit clear blue color. Furthermore, although the uses of these compounds are disclosed as ink-jet inks, no examples of using the compounds as color filters have been mentioned yet.